An oil field thief hatch is a closable hatch on an oil field tank or vessel. Thief hatches are typically used on low pressure and atmospheric tanks. The hatch allows for samples to be taken on the material inside, the volume of the tank to be measured, and for protecting the tank from over pressure and vacuum. Leaving the thief hatch open on a fuel storage tank can be very expensive. Fines vary from state to state with some fines being as much as $15,000 per hatch per date and these fines are ever increasing. Additionally, a hatch that appears closed, but is not latched will cost just as much in fines as one left fully open. It is thus desirable to provide a sensor system that can monitor the closed state of a thief hatch.
It is not easy to know if a hatch is fully latched as often these tanks are in the middle of a field and spaced far apart from one another. To check closure of the tank lid manual inspection is often necessary, which is time consuming and labor intensive, especially with hundreds of thousands of tanks in use. Other monitoring options include custom software sensing systems that tend to be extremely expensive and hard to install. It is thus desirable to provide a sensor system for monitoring thief hatches both new and existing with simple installation. It is also desirable to create a sensor system that can be retrofitted onto existing oil field tank lids with materials and procedures that can be used in the field.